Vulcanization controlling process



Patented July 24, 19 51 2,561,524 a VULCANIZATION CONTROLLING rnoonss George M. Massie, Cuyahoga Falls, Ohio, assignor Y to Harrison & Morton Laboratories, Inc., Guyahoga Falls, Ohio, a corporation. of Ohio No Drawing. Application July9, 1948,

Serial No. 37,975

9 Claims. (01. 260482) This invention relates to the art of vulcanizing rubber or rubber-like compounds and particularly to an improved processwherein there is employed a member of a preferred class of comvide a new class of compounds which will: (a)

tion is -bicyclo [2 2.- 1] -5 -heptene-2,3 -dicarboxylic effectively control the vulcanization of rubber by.

retarding incipient vulcanization at low temper atures with little or no such action at the later stages of vulcanization at higher temperatures,-

pounds which improves the action of the accel 5 (b) retard the initial cure at vulcanizing or high erator employed. in the vulcanization. More processing t p atu effectively control specifically, the preferred'classof compounds acts the scorchin effect of alkaline carbon blacks- V toretard incipient vulcanization or scorch dur- In its broad aspect, my invention involves the 'ingthe mixing, forming) and storage stages of discovery that materials such as bicyclol2 -2- 115- I the process and provide for the more ready hanpte arb y yd 0 its deriVa/f dling of the rubber stocks. In the later stage of tives function in the above manner. the curing process, 'the preferred class of com- The invention y be pr i y u s pounds donot exert such retarding action and her comp n s ont i n m ny different yp may. even accelerate the vulcanization. of organic vulcanization c l a among It is well known that many accelerators, which Which may be mentioned: p are particularly efiective in their accelerating ac- Type I' A1dehyde amineS-L tion and are otherwise desirable, are limited in Aceta1dehyde,ani1ine condensation prodtheir commercial application in certain processes ucts. for the reason that such rubber mixes into which Alpha ethyl t propyl i ili they are incorporated tend to prevulcanize or 1; scorch during the mixing operation or on storage Type 1 ofgthe compounded mix. The use of internal Dipheny1guanidjne mixers tends to elevate the temperature and in Diortho tolyl dm the further stages of processing, particularly in Type III --Thia,z01es: l the calendering and extruding operations, the a. z-mercaptobenzothiazola high temperatures encountered tend to cause 1 Zin benzothiazyl mde, prevulcanization. c. 2,2-benzothiazy1 disulfide.

As typical examples of accelerators which ex-, 03. Dinitro phenyl benzothiazyl sulfide. hibit a tendency v scorch in varying degrees are e. Phenyl aminomethyl Z-benzothiazyl sulthe mercaptobenzothiazoles and the dithiocarfide. bamates. Certain accelerators of the aldehyde- 1. Benzothiazyl 2 monocyclohexyl sulfen amine type, for example butyl aldehyde-aniline amide.

' condensation products, when used alone, are g. Dimethyl thiazyl disulfide comparatively inactive with regard to acceler- Type IV..-Thiazolines: ating action at temperatures below approximately a. Mercapto thiazoline. 220 F. These materials, however, may exhibit b. Zinc thiazolinyl sulfide. a relatively great tendency to scorch if processed Typ V.-Thiuram sulfides: at a higher temperature or if used in conjunction. a- T tra e y t iu am disulfi with an accelerator of the mercaptothiazole or Tetla methyl thiuram mOIlO S fi dijthi rb t type, 40 0. Di 5 N pentamethylene thiuram tetrasul- It has been recognized thatcertaintypes of f I accelerators of vulcanization become much more Type VI--D1th10ca1bamate$1 t Y active in the presence of certain types of carbon N'pentanlethylene ammonium Pentameths black. Among such accelerators may be meny it b m t tioned those of the mercaptothiazole and dithio- 45' bl Z1110 dlethyl l h lecarbarnate. carbamate type which becomemore active with Leafi P ammo ethyl) Phenyl dlmeth' alkaline type carbon blacks. The increase in ac- Y1 fi f tivity, when produced in this manner, takes place a Dmm'o phenyl dlmethyl dlthwcarbamateat lo e p atu e as w l as the usual c i The above list of materials servesonly to intemperatures so that rubber mixes containing dicate the scope of the invention and many modithese yp s f l rat rs a d an alkaline yp fications may be made. The preferred materials carbon black become difficult to handle due tol are also effective with two or more accelerators of f prevulcam'zation during processing or during the same type as well as with two or more. accelstorage of the compounded mix. t 1 erators of different type. t a i t It is the object of the present invention to pro-. The preferred compound of the present invenanhydride, but many other derivatives may be used, and function in like manner. Among those which may be mentioned is bicycloEZ-Z-ll-S- heptene-2,3-dicarboxylic acid, and the metallic salts of bicyclqiz j 2; ll -heptene-2,3 dicarboxylic acid such as caloiu-mlz' amine salts; and amine acid salts;

BicycloEZ-Z-l]-5-heptene-2;3-dicarboxylic an-* hydride may be prepared in accordance with the method described by Diels and Alder, Ann. V011,. 460, page 98 (1928) or more directly by reacting. maleic anhydride with dicyclopentadiene at a. temperature above 170 0,, preferably at 195 to 200" C. The dicyclopentadiene may be a relatively"impurecommercial grade. The resulting crude product obtained by heatingmaleic anhydridewith dicyclopentadiene" may be used as an impure'product or may be further purified.

The esters, iinidesjamine salts, amidic acids,

mo'no amidelamine' salts, and amine acid salts maybe prepared .by"suitable modification of the methods described byiLo wy et al., J Am. Chem. Soc. vol. (id'page 404? (1944). Monoesters may be conveniently prepared at low temperatures in accordance with the reaction'described by Siegel and Moranjibid vol 69, page 1457 (1947).

Bi'cy'clo heptene dicarboxylic anhydride may exi'st'i'n the endo'or exo configuration with re-' gard to the bicycle heptenering and in the cis and/or trans configuration with. regard to the carboxyl groups; Thecompoundas prepared in accordance with the method of Diels andAlder is predominately in theiendo-cis-configuration.

I do not wish to be bound, however, by method of preparation or by configuration, but desire to be protected by Letters-Patent, for the use of the materials for the purposes described.

The materials may be added-to the-rubber 0 rubber compound at other points in the milling or processing 'operations and still obtain beneficial results. I

In order to more-clearly illustrate my invention, the preferred modes of carrying the same into effect and the advantageous'results to be obtained thereby, thefollo'wing' examples are given: v

f YEXAMPLEI "This eiiampledemonstrat'es the use ofbicycIO- The stocks so compounded were vulcanized by heating in a press in the well-known manner for. varying periods of time at a temperature of 280 F. On testing the cured rubber product, the

w V 5 following results set forth in Table I were obmagnesium, lead,'aluminum, copper, iron, tin cadmium" and barium; the alkyl esters of primary alcohols, preferably wherein only one carboxyl group is esterified; the'-- i i amine salts including the guanidinesalts; the, N-substituted imides; amidic acids; -mono amide tainedi i 'ri Twbl" Mgdu1usl gff las tic- Cure t'ime Tensile Ult. 1 Y 7 Stock miputes at breakin Elong., elongatlons 01;

- 280 F. lbsi/in Percent of the curing process.i

. In order to-sh'ow the-retarding effects onin oling the Mooney viscometer described by M.

35 Mooney Industrial and Engineering Chemistrm-W- Anal. Ed, vol;- 6, page 147: 1934) --Relative scorch tendency'based on plasticity data was determined--- in accordance with the: :method 'described by svTaylor, Fieldingand Mooney, Rubber- Ag'eg vol r The time-required to cause incipient -vulcani- I zation of the .above three uncuredrubber -=sto'cks is shown in TableII.

, meat.

a -Minutes-re 1 Stock 7 if F. to cause 1 incipient This example d m nst ates the use bf bicyclfo v: [2-2-1] -'5 heptene-2,3-dicarb'oxylic' anhydride in f "a pure gum type stock accelerated with various [2-2-1]-5-heptene-2,3.-dicarboxylicanhyd'r'ide in ict) cceleratorsincluding' '2 ber fi it a l b a rubberstock accelerated with 2emercaptobenzothiazolef Three difierent stocks werecompounded, the

composition being" as follows:

type and one of thethijura compositions were as follows Stock 4A 100 10c, 4s 4s 1.. "gnu 1, a..."

in vulcanization:

The'stoeks *socompounded were vuleanized'in 1 Ta l V a press andthe -vu1eanized"product on testing Modulus 6f elasticity gave the following results set forth in Table III. oue time Tensile mt i1} lbsJmtat along? T bl In Stock mgswr, brealgin Elong., I a e Minutes lbs/1n. per cent 300 Per 5% Per Gent ent Cure Modulus of Tensile at Ult. elasticityin Stock break in E1ong., lbs/in. at 45 3'48) 520 1'590 3'340 Time, Temp lbs/in." percent elongations 45 3:630 1:555 3:340 Mmutes F 600% 4,355 500 1, 400 5, 360 .20 4,515 510 1,255 3,050 257 5,510 610 3,590 g g 238 f 32, 287 31495 a0 1 4350 600 1 420 3 365 so 257 3,880 730 1,855 1 1 1 1 Y 45 1 4, 010 610 1, 255 020 e 1' 20 4,390 680 1,175 2,920 ,Relatwe t1me requlred to jcause ncip ent vul 20 4,130 660 1,100 2, 595

cani'zation as determined in thejMoone'yyiscorneter on the uncured rubber stocks is setforth, in

Table Table 20 on the uncured rubber stocks is set forth in' m? 1 Table VI Minutes rei I Minutesrequired to quireclto Stock 1 causeitneipieizigbw- 081158111 Stock cipient vuleamza 10118! eanization A 21 at 250 F. B 50 o 25 1) 31.5 A 50 E 15.5 B 42 F- 21 0 25 306 37.5 1) 45 H 78 E 7 .T 25 r 10 K 33 L 9 r 1 I M 14.5 EXAMPLEIII. 35 3 52 1 1 P 15 This example demonstrates the use of bicyclo- R 23 [2'-2-1]-5-heptene-2,3-dicarboxylie anhydride in I: 1: a tread type stock containing accelerators of a E LE IV number of types. The compositions 'were as fol- This example demonstrates the use of bildws 40 Relative time required to cause incipient vulcanization determined in the Mooney viscometer cyclol2-z-ll-5-heptene- 2,3 -dicarboxylic anhy- Stock B C renJK Rubber (Smoked Sheets) EPO Black Zinc Oxide Stearic Avid Diphenyl Guenidine Zinc benzothiazyl sulfide Lead (phenylamino ethyl) phenyl di- 1 methyl dithiocarbamate Alpha ethyl beta propyl acrolein-Aniline Benzothiazyl 2-cyelohexyl sulfenamide. Z-mercapto thiaz oline 2-mercapto benzothiazole Diphenyl Guanidine Amine salt of dibutyl dithioearbamic acid. Bicyc1o[22-1]-5-hepte11e- 2,3-dicarboxylic anhydride 1 The stocks so compounded were Vulcanized by heating in a press at a temperature of 287 F. On testing the cured rubber products, the following results set forth in Table V were obtained.

dride in rubber stocks accelerated with Z-mercaptobenzothiazole and containing carbon blacks tions were as follows:

of different type and alkalinity. The composie,

Stock -Q...

Rubbersmoked Sheets) Sulfurm" B Bicyc1o[2-'2-1] 5 heptene -2,3 dicarboxylic anhydride B I The stocks so compounded were Vulcanized by heatingin a press at atemperature of 287 F. 011- testing the cured rubber :procluctthe following results set forthin Table VII were obtained.

Table'VII" tMldlflliiogplflzs-t Curetime Tensile at Ult. y m a j: Stock Minutes break in Elng Q PF at 287 F. lbs/in. percent Relative time required to cause incipient vulcanization determined in the Mooney viscometer issetrforth in Table V111.

' Table VIII M iiiu2tseg rg digired a Ste-ck --cause-incipient vulcanization It is thus seen from the data set forth in Table VIII that carbon blacks of relatively high alkalinity (e. g., H. M. F. "Black and F. F; Black) I have an activating effect-0n incipient vulcanization as compared to E. P. C; Black. Bicycloj- 4 5 [2-2-1]-5-heptene-2,3-dicarboxy1ic anhydride in effectively increasing the time required to'causel incipient vulcanization at processing'temperature, markedly increases processing safety. Inl j the case of SRF Black, the time required to cause incipient, vulcanization has been extended more than two-fold. a e I EXAMPLE vc This example demonstrates theuse'of bicycle- [2 2 11-5-heptene-2,3-dicarboxy1ic anyhydride, bicycle [2 2 1] -5-heptene-2,3 dicarboxy1ic acid,

Table Optestingthecured.rubbenproduct-thefollowing resultsi s etforthinTableIX- were obtained.

l. =\.e lative ,time required to cause incipient vulcanization, determined in the .Moone'y. viscometer. onthelnncured. rubber stocks is .set .forth in;

Table .X

Stock Ex MPLE V:

This example demonstrates the'use of bicycle- [2 2 1] -5-heptene-2,3-dicarboxylic anhydride as a retarder of incipi'entvulcanization at a number of different. temperatures. The temperatures employed 'fall' within the range encountered in practical mixing operation.

Two different stocks were compounded by the: so-called split-batch method, the composition] being as follows:

Parts by Weight Stock Rubber (SmokedSheets) -100 100 Zinc Oxide. i 10 Suliur 3' Stearie Acid 2 2-mercapto benzothiaz 1 I I Relative time required to cause incipient canization at different temperatures determined; 1 in the Mooney viscometeron the uncured rubber. v

and the mono methyl ester of bicycloi2-2-1l-5- heptene-2,3-dicarboxy1ic acid in a rubber stock accelerated with Z-mercapto loenz'othiazole.

The compositions were as follows:

sack A I B "The stocks so compounded; were vulcanizedby heatinginapressat atemperature ,of 287 F. hi5.

stocks isssetiorth in Table XI.

Table XI Percent MinuiaesJ impigovement require 0 in we re- Stock 23???? cause incipquired to lent vulcancause incipization ient vulcanization Per cent 220" 40 220 21. 2 250- 18 250 43 138. 8 280 8 280 15. 5 93. 7 300 5. 5 300 9 63. 6

This. example demonstrates the use of a num- Minutes required I 2- mercapto benzothiazolel were as follows:

if) 9 her of metallicybicyclo[2-2-1]-5 heptene-2,3dicarboxylates in a rubber stock accelerated with The compositions 10 of compounding ingredientsare readily apparent to one versed in the art.

WhatIclaimisz l. A process of treating a rubber compound Stool: A B O D E Rubber (Smoked Sheets) 100 100 100 100 100 100 EPO Black 48 18 48 48 48 48 Zinc Oxide 5 5 5 5 5 5 Stearic Acid 3 3 3 3 3 3 Sulfur 3 3 3 8 3 3 Paraflux. 2 2 2 2 2 2 Anfimridanr 1 1 1 1 1 1 Z-mercapto benzofhiamip 1 1 1 1 1 1 Zmcbicyclo[2-2-l]-5-heptene-2,3-dicarboxylate 0. 75 Calcium bicycle[2'2-1]-5-heptene-2,B-dicarboxylate. 0. 75 Barium bicyclo[2-2-l]-5-heptene-2,3-dicarboxylatc 0. 75 Cadmium bicyclo[2-2-1]-5-heptene-2,3-dicarboxylare 0. 75 Oupric bicyclo[2-2-l]-5-heptene-2,3-dicarboxylate 0. 75

The stocks so compounded were vulcanized by heating in a press at a temperature of 287 F. On testing the cured rubber product, the following results set forth in Table XII were obtained.

Relative time required to cause incipient vulcanization determined in the Mooney viscometer on the uncured rubber stocks is set forth in Table XIII.

TableXIII lvtinutes equir 0 cause mc1p1- Stock m; vulcanization at 250 F.

The preferred method of practicing the invention is to employ from 0.1 to 2.0% of the retarder material in the rubber composition but the quantity to be employed is dependent upon several considerations, such as (a) type of rubber composition, (b) amount of retardation desired, (0) accelerator employed, (d) retarder material employed.

In certain cases, it is advantageous to use the retarder materials mixed with other substances such as a finely divided solid or an oil. For certain cases, it is advantageous to use a mixture of two or more of the preferred materials.

The term rubber is to be construed broadly as rubber in the form of or derived from naturally occurring rubber dispersions or in the form of artificially prepared sulfur vulcanizable elastomers.

This invention is not restricted to the use of the particular materials disclosed in the specification, nor is it restricted to the use of the preferred class of materials in the particular rubber compositions herein described, since other rubber compositions employing a Wide Variety containin sulphur and organic accelerator, for controlling the vulcanization thereof, consisting in incorporating in the compound 0.1 to 2 percent of material selected from the group consisting of bicyclo[2.2.1]-5-heptene 2,3 dicarboxylic acid, the anhydride thereof, the aluminum, calcium, barium, magnesium, zinc, copper, iron, tin, lead and cadmium salts thereof, and the mono methyl ester thereof.

2. A process of treating a rubber compound containing sulfur and organic accelerator for controlling the vulcanization thereof consisting in incorporating in the compound 0.1 to 2 per cent of bicycle [2.2.1] -5-heptene-2,3-dicarboxylic anhydride.

3. A process of treating a rubber compound containing sulfur and organic accelerator for controlling the vulcanization thereof, consisting in incorporating in the compound 0.1 to 2 per cent of a metallic salt of bicyclo[2.2.1]-5-heptene-2,3- dicarboxylic acid where the metal is a member of the group consisting of aluminum, calcium, barium, magnesium, zinc, copper, iron, tin, lead, and cadmium.

4. A process of treating a rubber compound containing sulfur and organic accelerator for controlling the vulcanization thereof consisting in incorporating in the compound 0.1 to 2 per cent of mono methyl ester of bicyclo[2.2.1] 5-heptene- 2,3-dicarboxylic acid.

5. The process of retarding the vulcanization of rubber which comprises heating a mixture of rubber, sulfur, and an accelerator selected from the group consisting of mercapto benzothiazole and derivatives thereof in the presence of 0.1 to 2 per cent of bicyclo[2.2.l]-5-heptene-2,3-dicarboxylic anhydride.

6. A rubber composition retarded as to incipient vulcanization at elevated temperatures including sulfur, organic accelerator, and 0.1 to 2 per cent of bicyclo[2.2.1]-5-heptene-2,3-dicarboxylic anhydride.

'7. A process of preparing a rubber compound including sulfur and an organic accelerator designed to prevent vulcanization during the mixing and processing operations, consisting in incorporating into the rubber compound 0.1 to 2 per cent of bicyclo[2.2.1]-5-heptene-2,3-dicarboxylic anhydride.

8. The process of treating a rubber compound designed to retard the activating effect of carbon black on vulcanization at low temperatures, consisting in incorporating in the rubber, an organic accelerator, sulfur, carbon black, and as a retarder bicyclo[2.2.1l-5-heptene-2,3-dicarboxylic anhydride.

9. The process of retarding the vulcanization of rubber which comprises heating a mixture of 'rub'ber; sulfur and organio accelerator in the presence of 0.1 to 2 per-cent-of"bicyc1o[2-21]-5- heptene-2,3-dicarboxy1io anhydride:

GEORGEM; MASSIE'.

REFERENCES CITED The following references are of record in: the f file of this patent:

Number.

Gerhart et a1. July 1, 1947 

1. A PROCESS OF TREATING A RUBBER COMPOUND CONTAINING SULPHUR AND ORGANIC ACCELERATOR, FOR CONTROLLING THE VULCANIZATION THEREOF, CONSISTING IN INCORPORATION IN THE COMPOUND 0.1 TO 2 PERCENT OF MATERIAL SELECTED FROM THE GROUP CONSISTING OF BICYLO(2.2.1)-5-HEPTENE-2,3-DICARBOXYLIC ACID, THE ANHYDRIDE THEREOF, THE ALUMINUM, CALCIUM, BARIUM, MAGNESIUM, ZINC, COPPER, IRON, TIN, LEAD AND CADMIUM SALTS THEREOF, AND THE MONO METHYL ESTER THEREOF. 